In recent years, due to a demand for energy saving, a further reduction in power consumption is required of motors of air-conditioners, driving motors for electric vehicles, and so on in fields of electric apparatuses using non-oriented electrical steel sheets. Further, PWM (pulse width modulation) waveform controlling, on which harmonics are superimposed by an inverter, has become dominant in motor driving in place of ON-OFF controlling with electric current. Accordingly, a non-oriented electrical steel sheet has come to be required to have an excellent high-frequency characteristic.
Conventionally, for the purpose of improving a high-frequency core loss of a non-oriented electrical steel sheet, specific resistance has been increased by an increase of contents of Si, Al, and Cr, and a thickness of the non-oriented electrical steel sheet has been reduced as much as possible. These can reduce an eddy current loss.
However, in a non-oriented electrical steel sheet containing Cr, a Cr-based carbide precipitates during manufacturing processes, working processes after the manufacture, and so on, and then a core loss increases and is deteriorated. The Cr-based carbide sometimes precipitates during annealing in the manufacturing processes. Further, a customer side using a non-oriented electrical steel sheet sometimes performs combustion and disappearance of stamping oil, shrink fit for manufacturing a split core, strain relief annealing, and so on. These workings and so on are performed at relatively low temperatures of about 200° C. to 750° C., and during these workings, the Cr-based carbide sometimes precipitates to grain boundaries.
Therefore, in order to suppress the precipitation of the Cr-based carbide in the non-oriented electrical steel sheet containing Cr, an art to make Mo contained therein has been proposed (Patent Document 1). However, in the art, a content of expensive Mo is 0.05 mass % or more, resulting in a great increase in material cost.